The present invention is based on a transmitter for sending signals over wireless channels and a method of sending signals over wireless channels according to the definition of the species of the independent patent claims.
Predistortion of OFDM signals (OFDM=orthogonal frequency division multiplex), specifically according to the transfer properties of the amplifier in the transmitter, is already known from M. Schrader and N. Hentati “Reduktion von Auβerbandstrahlung von Sendestufen im DAB-COFDM-System [Reducing out-of-band radiation of transmitter stages in the DAB-COFDM system]” OFDM Fachgespräche, September 1998, Braunschweig, printed in the conference volume. This is necessary because OFDM signals require good linearity of the amplifier in the transmitter due to the great difference between the large and small amplitudes occurring in OFDM signals, i.e., the dynamics or amplitude variance, because all OFDM signal amplitudes are to be amplified linearly. The article referenced above describes a feedback system for predistortion, where a portion of the amplified OFDM signal is fed back and compared with a buffered OFDM signal to determine the transfer properties of the amplifier in the transmitter. The buffered OFDM signal is the OFDM signal which is then amplified and fed back. Since the properties of the OFDM signal are very similar to those of a noise signal, this requires high-quality synchronization of the buffered OFDM signal and the amplified OFDM signal.